RNA-editing of the 5-HT(2C) receptor alters agonist-receptor-effector coupling specificity.

Berg KA, Cropper JD, Niswender CM, Sanders-Bush E, Emeson RB, Clarke WP
Br J Pharmacol. 2001 134 (2): 386-92

PMID: 11564657 · PMCID: PMC1572953 · DOI:10.1038/sj.bjp.0704255

1. The serotonin(2C) (5-HT(2C)) receptor couples to both phospholipase C (PLC)-inositol phosphate (IP) and phospholipase A(2) (PLA(2))-arachidonic acid (AA) signalling cascades. Agonists can differentially activate these effectors (i.e. agonist-directed trafficking of receptor stimulus) perhaps due to agonist-specific receptor conformations which differentially couple to/activate transducer molecules (e.g. G proteins). Since editing of RNA transcripts of the human 5-HT(2C) receptor leads to substitution of amino acids at positions 156, 158 and 160 of the putative second intracellular loop, a region important for G protein coupling, we examined the capacity of agonists to activate both the PLC-IP and PLA(2)-AA pathways in CHO cells stably expressing two major, fully RNA-edited isoforms (5-HT(2C-VSV), 5-HT(2C-VGV)) of the h5-HT(2C) receptor. 2. 5-HT increased AA release and IP accumulation in both 5-HT(2C-VSV) and 5-HT(2C-VGV) expressing cells. As expected, the potency of 5-HT for both RNA-edited isoforms for both responses was 10 fold lower relative to that of the non-edited receptor (5-HT(2C-INI)) when receptors were expressed at similar levels. 3. Consistent with our previous report, the efficacy order of two 5-HT receptor agonists (TFMPP and bufotenin) was reversed for AA release and IP accumulation at the non-edited receptor thus demonstrating agonist trafficking of receptor stimulus. However, with the RNA-edited receptor isoforms there was no difference in the relative efficacies of TFMPP or bufotenin for AA release and IP accumulation suggesting that the capacity for 5-HT(2C) agonists to traffic receptor stimulus is lost as a result of RNA editing. 4. These results suggest an important role for the second intracellular loop in transmitting agonist-specific information to signalling molecules.

MeSH Terms (21)

Amphetamines Animals Arachidonic Acid Binding, Competitive Bufotenin CHO Cells Cricetinae Dose-Response Relationship, Drug Ergolines Inositol Phosphates Lysergic Acid Diethylamide Piperazines Protein Isoforms Quipazine Radioligand Assay Receptor, Serotonin, 5-HT2C Receptors, Serotonin RNA Editing Serotonin Serotonin Receptor Agonists Tritium

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